1. Field of the Invention
This invention relates to a light-condensing method and a light condenser and also to a near-field optical microscope and a storage device realized by applying such a light-condensing method and such a light condenser.
2. Related Background Art
Various microscopes and storage devices using optical near-field have been proposed along with exposure techniques also using an optical near-field (see, inter alia, Durig et al., J. Appl. Phys. 59, 3318 (1986), U.S. Pat. No. 6,171,730). Particularly, the exposure technique disclosed in U.S. Pat. No. 6,171,730 has contributed greatly to the related technical fields because of its excellence.
The known techniques mostly utilize an optical near-field generated from a micro-aperture or an optical near-field generated from a slit or a gap.
For example, microscopes using an optical near-field are adapted to bring an optical near-field generated from a slit by light from a light source close to the surface of a specimen arranged on a substrate and obtain an image of the surface of the specimen by using resultant scattering light. Storage devices of the above identified type are such that light from a light source is irradiated onto a recording medium and scattering transmitted light from a micro-aperture of a periodic structure formed on the surface of the recording medium is used for signal recording/reproduction.
Meanwhile, researches are being made to develop techniques for patterning the directions and the distributions of the electric field of light in propagating light and analyzing the behaviors of beams of light prepared in this way (see Ze'ev Bomzon et al., Appl. Phys. Lett. Vol 79, 1587 (2001)). Particularly, researches are being made on light whose electric field vectors are rotation-symmetric, radial and dimensionally equal at equidistant points from the center of symmetry.
However, with known near-field optical microscopes and storage devices, when photoelectric field is concentrated to such a micro-region by using an optical near-field generated from a micro-aperture of a periodic structure or a slit, the intensity distribution of the electric field of light generated in the vicinity of the emission port of the micro-aperture or the slit is dependent on the edge roughness and the aperture diameter of the micro-aperture or the slit to a great extent. Thus, conventionally, the controllability of the edge roughness and the machining precision for the diameter of the micro-aperture are required to an enhanced degree.